This section is intended to provide a background or context to the invention that is recited in the claims. The description herein may include concepts that could be pursued, but are not necessarily ones that have been previously conceived or pursued. Therefore, unless otherwise indicated herein, what is described in this section is not prior art to the description and claims in this application and is not admitted to be prior art by inclusion in this section.
Design of combustion systems is a complicated process that requires an in-depth knowledge and resolution of several factors, such as complex geometry, turbulent flow patterns, heat transfer and complex combustion-related chemistry. In order to design a safe and efficient combustion system, it is critical to accurately monitor and control the various aspects of the combustion process. In particular, the monitoring and prediction of environmental pollutants have become very important in the design of modern combustors. These pollutants may include nitrogen oxides (NOx), carbon monoxide (CO), carbon dioxide (CO2) and unburned hydrocarbons (UHC), and are subject to strict environmental emission regulations.
One of the strategies adopted by many modern gas turbine combustors for suppressing the emission of NOx, CO, CO2, UHC and other pollutants is to operate with a tightly controlled fuel/air ratio. In particular, a system with a very fuel-lean premixed flame (i.e., a dry low emission technology) is often utilized. The goal of such a system is to make the premixed flame as lean as possible without going below the Lean Blow-Off (LBO) limit. LBO is the point beyond which the fuel-air mixture is no longer flammable. Thus the desire to operate near the LBO limit must be balanced against the undesirable consequences of flame instability or extinction. In practice, fuel-lean premixed flames are very sensitive to their surrounding environment, and as such, it is advantageous to be able to efficiently and accurately assess the variations in the environment and fuel compositions in order to predict and monitor the LBO conditions. Furthermore, as the popularity of ‘opportunity’ fuels increases, engine designers may be routinely required to verify the impact of alternative fuels on operability, efficiency and emissions associated with the various combustion engines.